阅读说明：本技术 调节离子选择性电极的方法 (Method of conditioning ion selective electrodes ) 是由 谭雅·胡特尔 伊丽莎白·艾玛·尼尔 格热戈日·阿图尔·奥尔洛夫斯基 于 2020-03-25 设计创作，主要内容包括：描述了制备/预调节/调节/处理用于离子选择性电极电池的离子选择性电极(ISE)的方法。离子选择性电极电池包括ISE和参比电极(RE)。该方法包括：将ISE和第二电极暴露于包括离子的溶液；跨ISE和第二电极施加第一组电位差(PD)中的具有极性的第一PD；以及跨ISE和第二电极施加第二组差PD中的具有相反极性的第一PD。(Methods of preparing/preconditioning/conditioning/treating an Ion Selective Electrode (ISE) for an ion selective electrode cell are described. The ion selective electrode cell includes an ISE and a Reference Electrode (RE). The method comprises the following steps: exposing the ISE and the second electrode to a solution comprising ions; applying a first Potential Difference (PD) of a first set of PDs across the ISE and the second electrode, the first PD having a polarity; and applying a first PD of the second set of difference PDs having an opposite polarity across the ISE and the second electrode.)

1. A method of making an ion-selective electrode (ISE) for an ion-selective electrode cell comprising the ISE and a Reference Electrode (RE), the method comprising the steps of:

exposing the ISE and second electrode to a solution comprising ions;

applying a first Potential Difference (PD) of a first set of PDs across the ISE and the second electrode having a polarity; and

applying a first PD of a second set of PDs having an opposite polarity across the ISE and the second electrode;

optionally, wherein applying the first PD of the second set of PDs comprises applying the first PD of the second set of PDs within a time period after applying the first PD of the first set of PDs, wherein the time period is in the range of 0ms to 100s, 1 μ s to 100s, 10 μ s to 100s, 100 μ s to 100s, 1ms to 100s, preferably in the range of 1 μ s to 10s, 10 μ s to 10s, 100 μ s to 10s, 1ms to 10s, 100ms to 10s, more preferably in the range of 1 μ s to 5s, 10 μ s to 5s, 100 μ s to 5s, 1ms to 5s, 10ms to 5s, 100ms to 5s, 1s to 5s, for example 20 ms.

2. The method of the preceding claim, wherein applying the first PD of the first group of PDs and/or applying the first PD of the second group of PDs comprises, at least in part: initiating ion flux into and/or out of the ISE.

3. The method of any one of the preceding claims, wherein applying the first PD in the first group of PDs and/or applying the first PD in the second group of PDs comprises: applying the first PD of the first group of PDs having a magnitude that is at most a damage threshold of the ISE.

4. The method of any one of the preceding claims, wherein applying the first PD of the second group of PDs and/or applying the first PD of the first group of PDs comprises: at least partially removing excess surface charge of the ISE.

5. The method of any one of the preceding claims, wherein applying the first PD in the first group of PDs comprises: applying the first PD of the first group of PDs for a duration in the range of 1ms to 100s, preferably in the range of 100ms to 10s, more preferably in the range of 1s to 5 s; and/or

Applying the first PD in the second set of PDs comprises: applying the first PD in the second group of PDs for a duration in the range of 1ms to 100s, preferably in the range of 100ms to 10s, more preferably in the range of 1s to 5 s.

6. The method of any one of the preceding claims, wherein the first group of PDs comprises M PDs comprising the first PD of the first group of PDs, and/or wherein the second group of PDs comprises N PDs comprising the first PD of the second group of PDs, wherein M and N are natural numbers of at least 1, and wherein M + N is greater than or equal to 3, wherein the method comprises: alternately applying at least one PD of the first set of PDs and applying at least one PD of the second set of PDs.

7. The method of any of the preceding claims, wherein the first PD in the first group of PDs is constant and/or the first PD in the second group of PDs is constant.

8. The method according to any one of the preceding claims, wherein the ion-selective electrode cell comprises a Counter Electrode (CE), and wherein the method comprises: measuring a current between the ISE and CE while applying the first PD in the first group of PDs and/or while applying the first PD in the second group of PDs.

9. The method of any of the preceding claims, wherein the ISE comprises an ion selective coating.

10. The method according to any of the preceding claims, wherein the second electrode comprises and/or is a Counter Electrode (CE).

11. A method of determining the presence of ions in a solution using an ion-selective electrode cell comprising an ion-selective electrode (ISE) and a Reference Electrode (RE), the method comprising the steps of:

preparing an ISE according to any one of claims 1 to 10 using a solution; and

using the ion-selective electrode cell comprising the prepared ISE, the presence of the ions in the solution is determined, preferably within 300s of completing the step of preparing the ISE, for example by means of a potentiometer, by means of an ammeter and/or by impedance.

12. An Ion Selective Electrode (ISE) prepared according to the method of any one of claims 1 to 10.

13. An ion selective electrode cell comprising an Ion Selective Electrode (ISE) according to claim 12.

14. An apparatus for preparing an ion-selective electrode (ISE) for an ion-selective electrode cell comprising the ISE and a Reference Electrode (RE), wherein the apparatus is configured to:

applying a first Potential Difference (PD) of a first set of PDs across the ISE and a second electrode, the first PD having a polarity; and

applying a first PD of a second set of PDs having an opposite polarity across the ISE and the second electrode;

optionally, wherein the apparatus is configured to apply the first PD of the second group of PDs within a time period after applying the first PD of the first group of PDs, wherein the time period is in the range of 0ms to 100s, 1 μ s to 100s, 10 μ s to 100s, 100 μ s to 100s, 1ms to 100s, preferably in the range of 1 μ s to 10s, 10 μ s to 10s, 100 μ s to 10s, 1ms to 10s, 100ms to 10s, more preferably in the range of 1 μ s to 5s, 10 μ s to 5s, 100 μ s to 5s, 1ms to 5s, 10ms to 5s, 100ms to 5s, 1s to 5s, for example 20 ms.

15. An ion selective electrode cell assembly comprising:

an ion-selective electrode cell comprising an ion-selective electrode (ISE) and a Reference Electrode (RE); and

the apparatus of claim 14.

16. Use of an opposite polarity to tune an Ion Selective Electrode (ISE) to determine the presence of ions in solution.

Technical Field

The present invention relates to an ion-selective electrode for an ion-selective electrode cell. In particular, the invention relates to the preparation of ion-selective electrodes for ion-selective electrode cells for use in determining the presence of ions in solution using the prepared ion-selective electrodes.

Background

Generally, an Ion Selective Electrode (ISE), also known as a Specific Ion Electrode (SIE), is a transducer (also known as a sensor) that converts the ionic activity of selected ions in solution into an electrical response, such as potential, current, and/or impedance. ISE is used in an ion selective electrode cell comprising the ISE together with a reference electrode. Thus, the concentration of selected ions in the solution can be determined from the measured electrical response with reference to the reference electrode. ISE is used in analytical chemistry, environmental chemistry, food research, biomedical protocols, and biochemical/biophysical research, typically to measure ion concentrations in aqueous solutions.

Preferably, the ISE has a fast response time so that a steady or stable state is quickly reached for measurement, which is accurate and does not require calibration, thereby simplifying the analysis scheme. In particular, for point of care (POC) applications and consumer products, for example, it is important that measurements are done quickly to provide rapid results. A steady or steady state allows for more accurate measurements because, for example, time-dependent electrical responses can be averaged over several seconds to reduce system noise. However, if the baseline is unstable and/or varies over time, the measurement accuracy is reduced. To improve response time and/or baseline stability, it is often necessary to adjust the ISE prior to use. Typically, conditioning involves exposing the ISE to high concentrations of specific ions over a period of 12 to 72 hours.

For healthcare applications, such as the analysis of biological fluids (e.g., blood), a relatively slow response time will be accompanied by changes in the properties of the biological fluid during the measurement. For example, the blood may at least have begun to dry and coagulate during the typical 120s (seconds) required to reach a steady state of measurement. This is the determination of potassium (K) in whole blood samples⁺) Is particularly important because red blood cells are undergoing metabolic activity or platelet activation (both of which alter potassium levels) during coagulation.

Therefore, there is a need for improved ISE.

Disclosure of Invention

It is an object of the present invention, among other objects, to provide an ion selective electrode cell and a method of preparing an Ion Selective Electrode (ISE) for an ion selective electrode cell that at least partially obviates or mitigates at least some of the disadvantages of the prior art, whether identified herein or elsewhere. For example, it is an object of embodiments of the present invention to provide an ion selective electrode cell with faster response time, accuracy, precision and/or reproducibility. For example, it is an object of embodiments of the present invention to provide a method of preparing an Ion Selective Electrode (ISE) for an ion selective electrode cell, which method reduces manufacturing complexity and/or time and/or can be performed in situ.

A first aspect provides a method of preparing an Ion Selective Electrode (ISE) for an ion selective electrode cell, the ion selective electrode cell comprising the ISE and a Reference Electrode (RE), the method comprising the steps of:

exposing the ISE and the second electrode to a solution comprising ions;

applying a first Potential Difference (PD) having a polarity in a first set of PDs across the ISE and the second electrode; and

a first Potential Difference (PD) of a second set of PDs having an opposite polarity is applied across the ISE and the second electrode.

A second aspect provides a method of determining the presence of ions in a solution using an ion-selective electrode cell comprising an ion-selective electrode (ISE) and a Reference Electrode (RE), the method comprising the steps of:

preparing an ISE according to the first aspect using the solution; and

the presence of ions in solution is determined using an ion selective electrode cell comprising the prepared ISE, preferably within 300s of the completion of the step of preparing the ISE, for example by means of a potentiometer, by means of an ammeter and/or by impedance measurement.

A third aspect provides an Ion Selective Electrode (ISE) prepared according to the method of the first aspect.

A fourth aspect provides an ion-selective electrode cell comprising an ion-selective electrode (ISE) according to the third aspect and a Reference Electrode (RE).

A fifth aspect provides an apparatus for preparing an Ion Selective Electrode (ISE) for an ion selective electrode cell, the ion selective electrode cell comprising the ISE and a Reference Electrode (RE), wherein the apparatus is configured to:

applying a first Potential Difference (PD) of a first set of PDs across the ISE and the second electrode, the first PD having a polarity; and is

A first Potential Difference (PD) of a second set of PDs having an opposite polarity is applied across the ISE and the second electrode.

A sixth aspect provides an ion-selective electrode cell assembly or a kit for an ion-selective electrode cell assembly, comprising:

an ion-selective electrode cell comprising an ion-selective electrode (ISE) and a Reference Electrode (RE); and

the apparatus according to the fifth aspect.

A seventh aspect provides a use of in-situ opposite polarity to tune an ion selective electrode ISE.

Detailed description of the invention

According to the present invention, there is provided a method of preparing an ion selective electrode ISE for an ion selective electrode cell, as set forth in the appended claims. Also provided are methods of determining the presence of ions in a solution, ion-selective electrode cells, apparatus for preparing ion-selective electrodes ISE for ion-selective electrode cells, ion-selective electrode cell assemblies, kits for ion-selective electrode cell assemblies, and uses of the in situ opposite polarity to modulate ISE. Further features of the invention will be apparent from the dependent claims and the following description.

Method for preparing ion selective electrode ISE for ion selective electrode cells

A first aspect provides a method of preparing an ion-selective electrode (ISE) for an ion-selective electrode cell, the ion-selective electrode cell comprising the ISE and a Reference Electrode (RE), the method comprising the steps of:

exposing the ISE and the second electrode to a solution comprising ions;

applying a first Potential Difference (PD) of a first set of PDs across the ISE and the second electrode, the first PD having a polarity; and

a first Potential Difference (PD) of a second set of PDs having an opposite polarity is applied across the ISE and the second electrode.

In this way, the response time of an ion selective electrode cell including the prepared ISE is improved (e.g., reduced) as compared to conventional conditioning ISE as previously described and as further detailed below, while also eliminating conventional conditioning. It should be understood that the response time is the time before a measurement is made using a measurable ion selective electrode cell, for example when a stable signal is available or obtained, such as a potentiometer measurement, an amperometric measurement and/or an impedance measurement relating to the concentration of ions in the solution. Namely, the method involves: just before measuring the ion concentration, a voltage pulse (i.e. a first PD and a second PD having opposite polarities) is applied over the ISE, typically for a short duration of e.g. a few seconds. This allows the ISE to reach steady state, electrical balance and electrode surface wetting almost immediately, which results in a steady signal within a few seconds and improved sensor linearity over a clinically relevant range.

By eliminating conventional conditioning, a manufactured ion selective electrode cell including manufactured (i.e., dried) ISE can be quickly prepared for measurement (i.e., determination of ion presence). This simplifies the analysis schemes of ion selective electrode cells, which enables these analysis schemes to be more easily and/or widely deployed, for example for POC or field applications. Since robustness to prolonged soaking may not be required, the manufacturing cost and/or complexity of the ion-selective electrode cell may be reduced, which allows for example selection of a more cost-effective but lower resistance substrate for the ion-selective electrode cell. In addition, preconditioned (i.e., pre-soaked) ion-selective electrode cells with relatively short shelf life (i.e., shelf life) are avoided. By thereby improving the response time of an ion selective electrode cell comprising the prepared ISE, a quantitative and/or qualitative determination of the presence of ions in solution may be performed faster, which allows for higher efficiency and/or throughput while providing more responsive results. This is important for time-critical or time-sensitive samples to be analyzed, for example when monitoring the reaction or when the ongoing reaction increasingly inhibits or interferes with the analysis over time. For example, coagulation and/or drying of the blood inhibits or interferes with the analysis of ions of interest therein.

Further, the accuracy, precision, and/or reproducibility of the measurements (i.e., determination of ion presence) may be improved as compared to conventional methods of conditioning ion-selective electrode cells as previously described. In particular, the method of preparing an ion selective electrode cell according to the first aspect enhances nernst response and/or improves the linearity of ISE. In addition, since the response time of the ion selective electrode battery including the fabricated ISE is improved, more measurements can be performed while the signal is stable, thereby improving, for example, the Relative Standard Deviation (RSD) of the measurements.

Furthermore, the method of preparing an ion selective electrode cell according to the first aspect may be performed in situ. That is, an ion selective electrode cell may be prepared using a sample to be analyzed, wherein the sample to be analyzed provides a solution including ions, such that preparing ISE therein and measuring ions therein using the ion selective electrode cell are performed using the same solution. Thus, for example, preparation and measurement may be performed continuously. For example, an ion-selective electrode cell may be immersed in a sample to be analyzed, such as a liquid, suspension, slurry, or wetted particles, in which the ion-selective electrode cell is prepared, and then the presence of ions in the sample is determined. For example, a quantity of a sample to be analyzed may be deposited on an ion selective electrode cell, which is used to prepare the ion selective electrode cell, and the presence of ions in the sample is then determined. By way of example, to analyze K in a blood sample⁺The method according to the first aspect may be used to prepare ion selection using bloodSexual electrode cell, with subsequent, e.g. immediate, determination of K in blood⁺Presence of (a). In this way, K in the blood sample is simplified⁺Such that the analysis may be performed at POC, for example, by the patient.

In addition, the concentration polarization of ions at, for example, the solution-membrane interface is reduced due to the application of a potential difference of opposite polarity across the ISE and the second electrode. In particular, if the opposite polarity potential differences are of equal magnitude and/or duration, the concentration polarization of the ions is expected to be low or absent.

It will be appreciated that by applying a potential difference across the ISE and the second electrode, for example a first PD of the first group of PDs and/or a first PD of the second group of PDs, an induced current is provided therebetween, for example having a direction according to the polarity of the applied potential difference.

Accordingly, the method according to the first aspect may equally and/or similarly be described as a method of preparing an ion-selective electrode (ISE) for an ion-selective electrode cell, the ion-selective electrode cell comprising the ISE and a Reference Electrode (RE), the method comprising the steps of:

exposing the ISE and the second electrode to a solution comprising ions;

providing a first current having a direction in a first set of currents between the ISE and the second electrode; and

a first current of the second set of currents having an opposite direction is provided between the ISE and the second electrode.

ISE

The International Union of theory and Applied Chemistry (IUPAC) golden book defines electrochemical half-cells based on an ion selective electrode (also known as the working electrode) as an electrochemical sensor, as a thin or selective membrane of an identification element, and other half-cells corresponding to the zeroth (inert metal in redox electrolyte), 1 st, 2 nd and 3 rd classes. These devices differ from systems involving redox reactions (zeroth, 1 st, 2 nd and 3 rd type electrodes), although they typically comprise a type 2 electrode as an "internal" or "internal" reference electrode. The potential difference response has as its major component the Gibbs (Gibbs) energy change associated with perm-selective mass transfer across the phase boundary (by ion exchange, solvent extraction, or some other mechanism). The ion-selective electrode must be used in conjunction with a reference electrode (i.e., an "external" or "external" reference electrode) to form a complete electrochemical cell. The measured potential difference (ion-selective electrode versus external reference electrode potential) depends linearly on the logarithm of the activity of a given ion in solution. Note that: the term "ion-specific electrode" is not recommended. The term "obligatory" means that the electrode is not responsive to additional ions. The term "ion-selective" is more appropriately recommended because no electrode is truly specific to one ion. "selective ion-sensitive electrode" is a less frequently used term to describe an ion-selective electrode. "primary" or "primary" ions are those ions that the electrode is designed to measure. The most sensitive measurement of "primary" ions, such as nitrate ion-selective electrodes, can never be determined.

The IUPAC kini defines an ion selective electrode cell as an ion selective electrode along with a reference electrode. Typically, the cell contains two reference electrodes (internal and external) and a thin film or membrane recognition-transducing element. However, in addition to this conventional type of battery (solution contact on both sides of the membrane), there are also battery arrangements (all solid state and coated wire types) in line contact with one side of the membrane.

It will be appreciated that according to the definitions of these IUPAC gold book, ISE is thus an ion selective electrode and RE is a reference electrode.

There are four main types of ion-selective membranes used in ion-selective electrodes: glass, solid, liquid based and composite electrodes. In one example, the ISE comprises and/or is a glass film ISE, a solid ISE, a liquid-based ISE, or a composite electrode ISE.

Glass films are typically made of ion-exchange glasses (silicates or chalcogenides), but are generally suitable for some singly charged cations, such as H⁺、Na⁺And Ag⁺. Chalcogenide glasses also act on doubly charged metal ions (e.g., Pb)²⁺And Cd²⁺) Has selectivity.

The crystalline film is made of single-substance single crystals or polycrystals and gives good selectivity to ISE, since only ions that can introduce themselves into the crystal structure can interfere with the electrode response.

Ion exchange resin membranes are based on organic polymer membranes comprising specific ion exchange substances (resins). ISE using ion exchange resin membranes is widely used, including for the analysis of anions. The use of a specific resin allows the preparation of ISE for tens of different ions, both monoatomic and polyatomic. However, such ISE tends to have low chemical and physical durability and "survival time". Have been specially directed to various alkali metal ions (Li)⁺、Na⁺、K⁺、Rb⁺And Cs⁺) Alkali metal ISE was developed. Each alkali metal ion is encapsulated in a molecular cavity, the size of which is designed to match the ion. For example, polymer-based membranes comprising ionophores such as valinomycin or potassium ionophore III can be used to determine K⁺. Has been specially aimed at various alkali metal ions (Be)²⁺、Mg²⁺、Ca²⁺、Sr²⁺And Ba²⁺) Alkaline earth metal ISE was developed. Each alkali metal ion is encapsulated in a molecular cavity, the size of which is designed to match the ion. For example, a polymer-based membrane including an ionophore, such as magnesium ionophore I, may be used to determine Mg²⁺Or a polymer-based membrane including an ionophore such as calcium ionophore IV can be used to determine Ca²⁺。

Enzyme electrodes are not true ion-selective electrodes, but are generally considered to be within the subject of ion-specific electrodes. Such electrodes are characterized by a dual reaction mechanism in which an enzyme reacts with a specific substance, and the product of the reaction (usually H)⁺Or OH^-) Detection is by a true ISE (e.g. pH selective electrode). An example is a glucose selective electrode.

In one example, the ISE comprises a film selected from the group comprising: glass films, crystalline films, and ion exchange membranes, such as polymer based membranes.

Preparation of ion-selective electrodes

The method is to prepare an ion selective electrode cell, wherein the ion selective electrode cell comprises ISE and RE. It should be understood that the method is to prepare the ISE for potentiometer, galvanometer, and/or impedance measurement. In particular, the method of preparing the ISE may be considered or referred to as a method of conditioning, preconditioning or treating the ISE, however such conditioning is in contrast to conventional conditioning, as described herein.

Ion selective electrode cell

In one example, an ion selective electrode cell includes: ISE and RE disposed on a substrate, as described below; and respective traces for electrically coupling the ISE and RE to circuitry, such as potentiometer circuitry (e.g., including potentiometers) and/or current meter circuitry (also referred to as ammeter circuitry), such as provided by the ISE. Accordingly, it should be understood that the ion selective electrode cell does not include a potentiometer circuit (e.g., including a potentiometer) and/or an ammeter circuit. In this way, the cost and/or complexity of the ion-selective electrode cell may be reduced such that the ion-selective electrode cell may be a single use (i.e. disposable) ion-selective electrode cell which is electrically coupleable to a potentiometer circuit and/or an ammeter circuit, for example provided by an apparatus according to the fifth aspect. A two-electrode ion-selective electrode cell (i.e., comprising ISE and RE) may be used for potentiometric measurements. In one example, an ion selective electrode cell includes a Counter Electrode (CE) (also referred to as an Auxiliary Electrode (AE)). A three-electrode ion-selective electrode cell (i.e., including ISE, RE, and CE) may be used for potentiometer and/or amperometric measurements. In one example, the ion-selective electrode cell is a two-electrode ion-selective electrode cell comprising ISE and RE. In one example, the ion-selective electrode cell is a three-electrode ion-selective electrode cell comprising ISE, RE and counter electrode CE. In one example, the second electrode is RE or CE. In a preferred example, the ion-selective electrode cell is a three-electrode ion-selective electrode cell comprising ISE, RE and a counter electrode CE, wherein the second electrode is CE.

Nernst response

Generally, an ion selective electrode ISE is a transducer (also referred to as a sensor) that converts the ionic activity of a particular ion in solution into an electrical response (e.g., a potential). According to the nernst equation, the potential theoretically depends on the logarithm of the ion activity:

wherein the content of the first and second substances,

e is the expected potential;

E⁰is a standard potential;

r is the universal gas constant;

t is the absolute temperature;

Z_Iis the charge on an ion (also referred to as an ion of interest or primary ion);

f is the Faraday constant; and

a_Iis the activity of the ions in the solution.

Thus, if the ion activity a_IThe x10 change of (a) results in about a 60mV or 30mV change in potential E for monovalent and divalent ions, respectively, the ISE exhibits a nernst response. On the contrary, when the ion activity a is_IWith x10 changes of (a) resulting in significantly larger changes in the potential E, the ISE exhibits a supernernst response, e.g. over 60mV, 120mV, 240mV or even 700mV for monovalent ions.

Generally, the ionic activity a_IIs a measure of the "effective concentration" of ions in a mixture in the following sense: the chemical potential of the ions depends on the activity of the actual solution in the same way as it depends on the concentration of the ideal solution. However, in practice, the concentration of the ions is generally used, not the activity a of the ions_I。

Polymer-based ISE typically comprises: an ionophore that imparts selectivity to the membrane by forming a stable complex with the ion of interest; ion exchangers, which provide electrical neutrality and ensure permselectivity; and a polymer matrix that provides support and mechanical function to the membrane. Now, from the phase boundary potential E_PBDetermining the polymer baseISE response:

wherein the content of the first and second substances,

a_I，aqis the activity of the ion in the aqueous phase; and is

a_I，orgIs the activity of the ion in the organic phase.

To exhibit the Nernst response, the activity a of the ions in the majority of the organic phase_I，orgMust remain constant and independent of the sample. Thus, in this case, E_PBCan be simplified to the nernst equation:

conventionally, polymer-based ISE must be exposed to the ion of interest to allow the ionic carrier to sequester the ion of interest. This well-known conventional process, referred to as conditioning, involves exposing the ISE to a high concentration of ions of interest in solution in a process that can take 12 to 72 hours. During this time, the membrane becomes hydrated and ideally reaches equilibrium through an ion exchange process in which ions of interest from solution ideally completely replace ions of the same charge in the membrane. For cation selective membranes, this conventionally adjusted established equilibrium process can be represented by the following formula:

wherein the content of the first and second substances,

l is with an ion of interest I^z+A ligand forming an ion-ionophore complex, with a stoichiometry of n; and is

Is an ion exchanger made of lipophilic anionsIon R^-And cation M⁺And (4) forming.

Cation M⁺Will separate into aqueous phases and react with the ion of interest I^z+And (4) exchanging. Lipophilic anion R^-Will remain in the membrane to maintain electroneutrality and allow selective permeability. This long term regulation effectively prevents the practical and efficient use of these polymer-based ISEs.

Screen printing electrode

In one example, the ISE and/or RE are screen-printed electrodes (SPE), for example screen-printed on a substrate formed of a polymeric material, for example Polyester (PE), Polypropylene (PP), ceramic or paper. Other substrates are known. Typically, screen printing provides for the fabrication of SPEs in a reproducible, low cost, and disposable form, while allowing for easy incorporation of chemically functionalized materials. The screen printing process has three major advantages over conventional electrode manufacturing methods: the electrode area, the electrode thickness and the electrode composition are easy to control; providing statistical validation of experimental results by repeated electrodes; and a catalyst may be added to the screen printing ink (paste). However, screen printing is generally limited to planar substrates.

In one example, the ISE includes and/or is formed at least in part from carbon, gold, and/or platinum. Preferably, the ISE comprises and/or is formed at least in part from carbon, for example by screen printing a carbon ink onto the substrate.

In one example, the ISE includes an ion selective coating, such as carbon, gold, and/or platinum coating. In one example, the ion-selective coating comprises a polymeric film providing a matrix, for example a neutral carrier based solvent polymeric film, for example plasticized polyvinyl chloride (poly (vinyl chloride), PVC), polyurethane or a UV curable resin (e.g. PU acrylate with acrylic monomers), including an ionophore, for example valinomycin, potassium ionophore III, magnesium ionophore I or calcium ionophore IV.

In a preferred example, the ISE comprises carbon and an ion-selective coating overlying the carbon, wherein the ion-selective coating comprises a polymeric film providing a matrix, for example a neutral support-based solvent polymeric film, for example a plasticized polyvinyl chloride (PVC), polyurethane or UV curable resin (e.g. PU acrylate with acrylic monomers), including an ionophore, for example valinomycin, potassium ionophore III, magnesium ionophore I or calcium ionophore IV.

In one example, the RE includes and/or is an Ag or Ag/AgCl reference electrode. In a preferred example, the RE is an Ag/AgCl reference electrode, for example, provided by screen printing an Ag/AgCl ink onto a substrate. In one example, the RE comprises and/or is a solid RE, e.g. based on doped conjugated and redox polymers, polymer composites and/or polymer electrolytes, e.g. derivatives of polypyrrole, polyamine and/or polythiophene. In one example, RE comprises and/or is Poly (3,4-ethylenedioxythiophene) (PEDOT) doped with Poly (styrene sulfonate), PSS) reference electrode. Other REs are known, including metal and/or carbon REs, such as saturated calomel electrodes, copper-copper (II) sulfate electrodes, palladium-hydrogen electrodes, and mercury-mercurous sulfate electrodes.

In one example, the ion selective electrode cell includes a Counter Electrode (CE). In one example, the CE includes and/or is formed at least in part of carbon, gold, and/or platinum, as described with respect to ISE. In a preferred example, the CE comprises and/or is formed at least in part from carbon, for example by screen printing a carbon ink onto the substrate, as described in relation to ISE. In one example, the CE is uncoated (i.e., as opposed to ISE).

Exposing

The method comprises the following steps: the ISE and the second electrode are exposed to a solution comprising ions. It should be understood that exposing the ISE and the second electrode to the solution including ions includes electrically coupling the ISE and the second electrode via the solution including ions. For example, a solution including ions may wet the ISE, the second electrode, and between them. For example, a solution comprising ions, such as a droplet or a layer thereof, may extend from the ISE to the second electrode. For example, the ISE and second electrode may be immersed in a solution containing ions.

In one example, exposing the ISE and the second electrode to the solution including ions includes electrically coupling (e.g., electronically, ionically, cationically, and/or anionically) the ISE and the second electrode via the solution including ions. In one example, exposing the ISE and the second electrode to the solution comprising ions comprises and/or by contacting, e.g., wetting, the ISE and the second electrode with the solution comprising ions. In one example, exposing the ISE and the second electrode to a solution comprising ions comprises and/or is deposited onto the ion selective electrode cell from the ISE towards the second electrode by depositing a solution comprising ions, e.g. droplets or a layer thereof. In one example, exposing the ISE and the second electrode to the solution comprising ions comprises and/or is performed by immersing the ISE and the second electrode in the solution comprising ions.

In one example, the ion selective electrode cell comprises a CE, and the method comprises: the CE is exposed to a solution comprising ions, as described with respect to ISE and/or RE. In a preferred example, the second electrode is CE.

Ion(s)

In one example, the ion is a monovalent ion, such as a monovalent cation or a monovalent anion. In one example, the ion is an alkali metal cation, such as Li⁺、Na⁺、K⁺、Rb⁺Or Cs⁺. In one example, the ion is an alkaline earth metal cation, e.g., Be²⁺、Mg²⁺、Ca²⁺、Sr²⁺、Ba²⁺Or Ra²⁺. In one example, the ion is a transition metal cation (e.g., a cation of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, or Zn) or a second row transition metal cation (e.g., a cation of Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, or Cd) or a heavy metal cation (e.g., a cation of Pb).

In one example, the ion is a monovalent anion (e.g., F)^-、Cl^-、Br、I^-、CN^-、NO₃ ^-Or HCO₃ ^-) Divalent anions (e.g. HPO)₄ ^2-、S^2-Or SO₄ ^2-) Or a trivalent anion (e.g. PO)₄ ^3-)。NO₃ ^-、PO₄ ^3-And/or K⁺It is usually measured for soil testing, as these macronutrients are important for plant growth. For example Mg²⁺、Cu²⁺And/or Zn²⁺The micronutrients of (a) may also be measured against soil tests.

Solutions of

In one example, the solution is an aqueous solution. In one example, the solution is part of a suspension, slurry, or mixture. In one example, the solution is a sample, such as an environmental chemical, food research, biomedical, biochemical, or biophysical sample. In one example, the solution is provided by a biological fluid, such as blood, whole blood, plasma, serum, urine, mucus, saliva, and/or sweat.

A first PD in the first group of PDs

The method comprises the following steps: a first PD of the first set of PDs having a polarity is applied across the ISE and the second electrode. It is to be understood that the ISE and RE are exposed to the solution including ions while a first PD of the first set of PDs having a polarity is applied across the ISE and the second electrode, wherein the ISE and RE are electrically coupled via the solution including ions.

In one example, a first PD of the first set of PDs includes a portion, e.g., a positive portion or a negative portion, of a waveform, e.g., a unidirectional, bidirectional, periodic, non-periodic, symmetric, asymmetric, simple, and/or complex waveform, e.g., a sinusoidal waveform, a rectangular waveform, a square waveform, a pulse waveform, a ramp waveform, a sawtooth waveform, and/or a triangular waveform. Other waveforms are known. In one example, the first set of PDs includes M PDs including the first PD, where M is a natural number of at least 1, such as 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, or more. The M PDs in the first group of PDs may be as described with respect to the first PD in the first group of PDs. Alternatively, the M PDs in the first group of PDs may have mutually different amplitudes and/or durations.

First PD in second group PD

The method comprises the following steps: a first PD of the second set of PDs having an opposite polarity is applied across the ISE and the second electrode.

It is to be understood that the ISE and the second electrode are exposed to the solution comprising ions while the first PD of the second set of PDs having a polarity is applied across the ISE and the second electrode, wherein the ISE and the second electrode are electrically coupled via the solution comprising ions.

It should be appreciated that the opposite polarity of the first PD in the second group of PDs is thus opposite to the polarity of the first PD in the first group of PDs. For example, if the polarity of a first PD in the first group of PDs is positive, the opposite polarity of the first PD in the second group of PDs is therefore negative. Conversely, if the polarity of the first PD in the first group of PDs is negative, the opposite polarity of the first PD in the second group of PDs is therefore positive. In other words, the method comprises: a PD of opposite polarity is applied across the ISE and the second electrode.

In one example, a first PD of the second set of PDs includes a portion, e.g., a positive portion or a negative portion, of a waveform, e.g., a unidirectional, bidirectional, periodic, non-periodic, symmetric, asymmetric, simple, and/or complex waveform, e.g., a sinusoidal waveform, a rectangular waveform, a square waveform, a pulse waveform, a ramp waveform, a sawtooth waveform, and/or a triangular waveform. Other waveforms are known. In one example, the second set of PDs includes N PDs including the first PD, where N is a natural number of at least 1, such as 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000 or more. The N PDs in the second group of PDs may be as described with respect to the first PD in the second group of PDs. Alternatively, the N PDs in the second group of PDs may have mutually different amplitudes and/or durations.

It is to be understood that the step of applying the first PD of the second group of PDs having an opposite polarity across the ISE and the second electrode may be performed before and/or after the step of applying the first PD of the first group of PDs having a polarity across the ISE and the second electrode. For example, a positive voltage may be applied across the ISE and the second electrode followed by a negative voltage applied across the ISE and the second electrode, or vice versa.

In one example, a method comprises: the first PD of the first group of PDs and the first PD of the second group of PDs are applied to provide a bi-directional, symmetrical or asymmetrical rectangular or square waveform, preferably a bi-directional, asymmetrical rectangular waveform.

In one example, the first group of PDs comprises M PDs including their first PD, and/or wherein the second group of PDs comprises N PDs including their first PD, wherein M and N are natural numbers of at least 1, and wherein M + N is greater than or equal to 3, wherein the method comprises: at least one PD in the first group of PDs and at least one PD in the second group of PDs are applied alternately. In other words, the respective PDs of the first and second groups of PDs may be applied alternately.

In one example, a method comprises: the M PDs in the first group of PDs and the N PDs in the second group of PDs are alternately applied to provide a bidirectional, symmetrical or asymmetrical rectangular wave or square wave, preferably a bidirectional, asymmetrical rectangular wave.

In one example, the first PD of the first group of PDs is constant and/or the first PD of the second group of PDs is constant.

In one example, applying the first PD of the first group of PDs and/or the first PD of the second group of PDs includes, at least in part, initiating ion flux into and/or out of the ISE. Without wishing to be bound by any theory, the amplitude of the first PD in the first group of PDs and/or the first PD in the second group of PDs should be large enough to initiate ion flux into the membrane such that the membrane can be electrically preconditioned and, to a large extent, becomes accessible to ions. It will be appreciated that the ion flux that initiates entry and/or exit from the ISE depends on the polarity and whether the ions are anionic or cationic.

In one example, applying the first PD of the first group of PDs and/or the first PD of the second group of PDs includes applying the first PD of the first group of PDs having a magnitude of a damage threshold of at most ISE. Without wishing to be bound by any theory, although the amplitude of the first PD in the first group of PDs and/or the second group of PDs should be large enough to initiate the ion flux, as described above, the amplitude of the first PD in the first group of PDs and/or the second group of PDs should not be so large as to damage the membrane, e.g., its surface.

In one example, applying the first PD of the second set of PDs and/or the first PD of the first set of PDs includes at least partially removing excess surface charge of the ISE. Without wishing to be bound by any theory, this step may remove excess surface charge (e.g., surface charge generated by a discharge capacitor created by a double layer of the membrane and solution), and/or minimize potential drift during electrical response measurements, such as potential (e.g., Open Circuit Potential (OCP) (i.e., potentiometer) measurements, current measurements, and/or impedance measurements.

In one example, applying the first PD of the second set of PDs and/or the first PD of the first set of PDs includes applying the first PD of the second set of PDs and/or the first PD of the first set of PDs having an amplitude in a range of ER/8 to 8xER, preferably in a range of ER/4 to 4xER, more preferably in a range of ER/2 to 2xER, more preferably in a range of 3xER/4 to 5xER/4, most preferably in a range of 7xER/8 to 9xER/8, wherein ER is the electrical response of the ion-selective electrode cell due at least in part to ions. In one example, applying the first PD of the second group of PDs and/or the first PD of the first group of PDs comprises applying the first PD of the second group of PDs and/or the first PD of the first group of PDs having an amplitude in the range of OCP/8 to 8xOCP, preferably in the range of OCP/4 to 4xOCP, more preferably in the range of OCP/2 to 2xOCP, more preferably in the range of 3xOCP/4 to 5xOCP/4, most preferably in the range of 7xOCP/8 to 9xOCP/8, wherein OCP is the open circuit potential OCP between ISE and RE due at least in part to ions. For example, if the expected OCP is 200rnV, the first PD of the first group of PDs and/or the first PD of the second group of PDs may have a magnitude in the range of 25mV to 1600mV, preferably in the range of 50mV to 800mV, more preferably in the range of 100mV to 200mV, even more preferably in the range of 150mV to 250mV, and most preferably in the range of 175mV to 225 mV. Without wishing to be bound by any theory, the amplitude of the first PD in the first group of PDs and/or the first PD in the second group of PDs is preferably as close as possible to the electrical response, e.g. OCP, in order to avoid interfering ion balances near the membrane that may initiate unwanted potential drift during the measurement of the electrical response (e.g. OCP). In one example, applying the first PD of the second group of PDs and/or the first PD of the first group of PDs comprises applying the first PD of the second group of PDs and/or the first PD of the first group of PDs having a magnitude in a range of 0.1mV to 5000mV, preferably in a range of 1mV to 1000mV, more preferably in a range of 10mV to 750mV, more preferably in a range of 50mV to 500mV, most preferably in a range of 100mV to 250 mV. In one example, the first PD of the second set of PDs and/or the maximum amplitude of the first PD of the first set of PDs is determined at least in part from the solution, e.g., to reduce and/or avoid oxidation and/or reduction of a solvent included in the solution. For example, for an aqueous solution, the maximum amplitude may correspond to a standard potential of-1.23V vs. Ag/AgCl for a water electrolyser at 25 deg.C, pH 0.

In one example, applying the first PD of the first set of PDs comprises applying the first PD of the first set of PDs for a duration in a range of 1 μ s to 100s, 10 μ s to 100s, 100 μ s to 100s, 1ms to 100s, preferably in a range of 1 μ s to 10s, 10 μ s to 10s, 100 μ s to 10s, 1ms to 10s, 100ms to 10s, more preferably in a range of 1 μ s to 5s, 10 μ s to 5s, 100 μ s to 5s, 1ms to 5s, 10ms to 5s, 100ms to 5s, 1s to 5s, for example 3 s; and/or

Applying the first PD of the second set of PDs comprises applying the first PD of the second set of PDs for a duration in the range of 1 μ s to 100s, 10 μ s to 100s, 100 μ s to 100s, 1ms to 100s, preferably in the range of 1 μ s to 10s, 10 μ s to 10s, 100 μ s to 10s, 1ms to 10s, 100ms to 10s, more preferably in the range of 1 μ s to 5s, 10 μ s to 5s, 100 μ s to 5s, 1ms to 5s, 10ms to 5s, 100ms to 5s, 1s to 5s, e.g. 3 s.

In one example, applying the first PD of the second set of PDs comprises applying the first PD of the second set of PDs within a time period after applying the first PD of the first set of PDs, wherein the time period is in a range of 0ms to 100s, 1 μ s to 100s, 10 μ s to 100s, 100 μ s to 100s, 1ms to 100s, preferably in a range of 1 μ s to 10s, 10 μ s to 10s, 100 μ s to 10s, 1ms to 10s, 100ms to 10s, more preferably in a range of 1 μ s to 5s, 10 μ s to 5s, 100 μ s to 5s, 1ms to 5s, 10ms to 5s, 100ms to 5s, 1s to 5s, for example 20 ms. In other words, the period includes and/or is a delay. That is, applying the first PD of the second group of PDs may be applied shortly after, preferably immediately after, applying the first PD of the first group of PDs.

In one example, a method comprises: the current between the ISE and the second electrode is measured while applying the first PD of the first group of PDs and/or while applying the first PD of the second group of PDs. In one example, the ion selective electrode cell comprises a counter electrode CE, and the method comprises: the current between the ISE and the CE is measured while applying the first PD of the first group of PDs and/or while applying the first PD of the second group of PDs. The inventors have determined that the measured current can provide useful information about the ionic activity of the solution and/or about ISE, RE and/or CE. This information may be used to calibrate the ion selective electrode cell (i.e., self-calibrate, auto-calibrate) and/or to correct the solution and/or ISE, RE, and/or CE, for example due to manufacturing tolerances.

Control of

In one example, applying the first PD of the first group of PDs having a polarity across the ISE and the second electrode includes controlling the first PD of the first group of PDs, e.g., according to a threshold, a desired PD profile as a function of time, and/or feedback, e.g., from a potential difference, current, and/or impedance measured while applying the first PD of the first group of PDs. In other words, applying the first PD of the first group of PDs may be voltage controlled. In this way, the ion-selective electrode cell may be prepared separately, for example according to its design or manufacture, to take into account deterioration (i.e. aging) during storage and/or to take into account ions and/or solutions in particular. Instead, in one example, the method includes: providing a first current of the first set of currents having a direction between the ISE and the second electrode, wherein providing the first current of the first set of currents comprises controlling the first current of the first set of currents, e.g. according to a threshold value, a desired current distribution as a function of time, and/or e.g. feedback from a potential difference, current and/or impedance measured when applying the first PD of the first set of PDs. In other words, providing a first current of the first set of currents may be current controlled. Impedance control may be similarly provided. The application of a first potential difference PD of opposite polarity in the second set of PDs across the ISE and the second electrode and/or the provision of a first current of opposite direction in the second set of currents between the ISE and the second electrode may be similarly controlled as described above with respect to the first PD in the first set of PDs and the first current of the first set of currents, respectively.

Preferred examples

In a preferred example, a method of making an ion-selective electrode ISE for an ion-selective electrode cell, the ion-selective electrode cell comprising the ISE and a reference electrode RE, the method comprising the steps of:

exposing the ISE and the second electrode to a solution comprising ions;

applying a first PD of a first set of potential differences PD having a polarity across the ISE and the second electrode; and

applying a first PD of a second set of potential differences PD having an opposite polarity across the ISE and the second electrode;

among these, ISE is a solid ISE with an ion-selective coating, such as an ion-exchange resin membrane, preferably a polymer-based membrane, for example based on plasticized polyvinyl chloride (PVC), polyurethane or UV-curable resins (e.g. PU acrylates with acrylic monomers), including ionophores, such as valinomycin, potassium ionophore III, magnesium ionophore I or calcium ionophore IV;

wherein the ion selective electrode cell is a three electrode ion selective electrode cell comprising ISE, RE and a counter electrode CE, wherein the second electrode is CE;

wherein the ISE, RE and/or CE at least partially comprises and/or is formed from carbon, gold and/or platinum, for example wherein the ISE, RE and/or CE is a screen printed electrode SPE which at least partially comprises and/or is formed from carbon, preferably by screen printing a carbon ink on the substrate;

wherein RE comprises and/or is an Ag or Ag/AgCl reference electrode; and is

Wherein exposing the ISE and the second electrode to a solution comprising ions comprises wetting the ISE, the second electrode and therebetween.

Method for determining the presence of ions in a solution

A second aspect provides a method of determining the presence of ions in a solution using an ion-selective electrode cell comprising an ion-selective electrode ISE and a reference electrode RE, the method comprising the steps of:

preparing an ISE according to the first aspect using the solution; and

the presence of ions in solution is determined, for example by a potentiometer, by an ammeter and/or by impedance, using an ion selective electrode cell comprising the prepared ISE, preferably within 300s of the completion of the step of preparing the ISE.

Thus, the ISE according to the first aspect is prepared by using a solution, followed by determining the presence of ions in the solution, e.g. by means of a potentiometer, galvanometer and/or impedance, as described above, whereby the preparation is performed in situ, while the response time, accuracy, precision and/or reproducibility of the measurement is improved, as described above.

The determining of the presence of ions in a solution using an ISE, a solution, an ion selective electrode cell, an ISE, a RE sensor and/or using an ISE, for example by a potentiometer, by an ammeter and/or by impedance, may be as described in relation to the first aspect.

In one example, the determination of the presence of ions in solution using an ion selective electrode cell, e.g. by a potentiometer, by an ammeter and/or by an impedance, is within 300s, preferably within 120s, more preferably within 60s, even more preferably within 30s, most preferably within 10s, e.g. within 5s, 4s, 3s, 2s or 1s of the complete preparation of the ion selective electrode cell. That is, determining the presence of ions in a solution may be performed shortly after, preferably immediately after, the preparation of an ion selective electrode cell.

Ion selective electrode

A third aspect provides an ion selective electrode ISE made according to the first aspect. The ion selective electrode cell, ISE, RE and/or second electrode may be as described in relation to the first aspect and/or the second aspect.

Thus, by using a solution to prepare an ISE according to the first aspect and subsequently determining the presence of ions in the solution using an ion selective electrode cell, for example by means of a potentiometer, by means of an ammeter and/or by means of impedance, as described above, the response time, accuracy, precision and/or reproducibility of the measurement is improved.

Ion selective electrode cell

A fourth aspect provides an ion-selective electrode cell comprising an ion-selective electrode ISE according to the third aspect and a reference electrode RE.

The ion selective electrode cell, ISE, RE and/or second electrode may be as described in relation to the first, second and/or third aspect.

Device

A fifth aspect provides an apparatus for preparing an Ion Selective Electrode (ISE) for an ion selective electrode cell, the ion selective electrode cell comprising the ISE and a reference electrode RE, wherein the apparatus is configured to:

applying a first Potential Difference (PD) of a first set of PDs across the ISE and the second electrode, the first PD having a polarity; and is

A first PD of the second set of PDs having an opposite polarity is applied across the ISE and the second electrode.

The ion selective electrode cell, ISE, RE, second electrode, the first PD of the first group of PDs having a polarity and/or the first PD of the second group of PDs having an opposite polarity may be as described with respect to the first, second, third and/or fourth aspect.

In one example, the device includes a power supply configured to apply a first potential difference PD of a first set of PDs across the ISE and the second electrode having a polarity and/or a first potential difference PD of a second set of PDs across the ISE and the second electrode having an opposite polarity.

In one example, an apparatus includes a controller, e.g., including a processor and a memory, configured to control a first Potential Difference (PD) of a first set of PDs across an ISE and a second electrode having a polarity and/or a first potential difference PD of a second set of PDs across the ISE and the second electrode having an opposite polarity.

In one example, the apparatus comprises a potentiometer for measuring a voltage across the ISE and the second electrode, an ammeter for measuring a current between the ISE and the second electrode, and/or means for measuring an impedance of the ion selective electrode cell.

Ion selective electrode battery assembly

A sixth aspect provides an ion-selective electrode cell assembly or a kit for an ion-selective electrode cell assembly, comprising:

an ion-selective electrode cell comprising an ion-selective electrode (ISE) and a Reference Electrode (RE); and

the apparatus according to the fifth aspect.

Use of

A seventh aspect provides the use of in situ opposite polarity to tune an Ion Selective Electrode (ISE) for determining the presence of ions in solution. In this way, response time and/or baseline stability of the ISE may be improved. In contrast to conventional methods of modulating ISE, methods involve exposing ISE to high concentrations of specific ions in a process that can take 12 to 72 hours; applying an opposite polarity to the ISE in the same solution as the defined ions (i.e. in situ); effectively modulate ISE, as described herein.

Definition of

Throughout the specification, the term "comprising" is intended to include the named components, but does not exclude the presence of other components. The term "consisting essentially of … …" is intended to include the specified components, but to exclude other components other than the materials present as impurities, inevitable materials present as a result of the process for providing the components, and components (e.g., colorants and the like) added for the purpose other than achieving the technical effects of the present invention.

The term "consisting of … …" is intended to include the specified component but exclude other components.

Use of the term "comprising" may also include the meaning of "consisting essentially of … …" and may also include the meaning of "consisting of … …" at any appropriate time depending on the context.

The optional features set out herein may be used alone or in combination with one another where appropriate, and especially in the combinations set out in the appended claims. Optional features of various aspects or exemplary embodiments of the invention as described herein may also be applied to all other aspects or exemplary embodiments of the invention, where appropriate. In other words, a person reading this specification should consider various aspects of the invention or optional features of example embodiments to be interchangeable and combinable between different aspects and example embodiments.

Drawings

For a better understanding of the present invention, and to show how exemplary embodiments thereof may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

fig. 1 schematically depicts a method of preparing an ion-selective electrode ISE for an ion-selective electrode cell according to an exemplary embodiment;

FIG. 2 schematically depicts the method of FIG. 1 in more detail;

fig. 3 shows a graph of measured OCP over time for an ion-selective electrode cell prepared according to the method of fig. 1 using ink a and a comparative ion-selective electrode cell;

fig. 4A and 4B show log [ K ] of an ion-selective electrode cell prepared according to the method of fig. 1 using ink a and a comparative ion-selective electrode cell⁺]A plot of the measured OCP (as measured and normalized, respectively) of the variation;

fig. 5A and 5B show log [ K ] of an ion-selective electrode cell prepared according to the method of fig. 1 using ink B and a comparative ion-selective electrode cell⁺]A plot of the measured OCP (as measured and normalized, respectively) of the variation;

fig. 6A and 6B illustrate ion selection prepared according to the method of fig. 1 using ink CLog [ K ] for a sexual electrode cell and a comparative ion selective electrode cell⁺]A plot of the measured OCP (as measured and normalized, respectively) of the variation;

fig. 7 shows a graph of the current measured between ISE and CE for an ion selective electrode cell prepared according to the method of fig. 1;

FIG. 8 schematically depicts an ion selective electrode cell according to an exemplary embodiment;

FIG. 9 schematically depicts an ion selective electrode cell according to an exemplary embodiment;

FIG. 10 schematically depicts an electrical circuit of an ion selective electrode cell according to an exemplary embodiment;

FIG. 11 schematically depicts an electrical circuit of an ion selective electrode cell according to an exemplary embodiment;

fig. 12 schematically depicts an exploded perspective view of an ion selective electrode cell according to an example embodiment;

figure 13 schematically depicts an example of applying a potential difference for the method of figure 1 in more detail;

FIG. 14A schematically depicts an electrical circuit of an ion selective electrode cell according to an exemplary embodiment; and fig. 14B schematically depicts a potential gradient in the ion selective electrode cell of fig. 14A;

FIG. 15A schematically depicts an electrical circuit of an ion selective electrode cell according to an exemplary embodiment; and fig. 15B schematically depicts a potential gradient in the ion selective electrode cell of fig. 15A;

FIG. 16 schematically depicts an electrical circuit of an ion selective electrode cell according to an example embodiment;

fig. 17A shows a photograph of 6 ion selective electrode cells prepared according to the method of fig. 1; and figure 17B shows a plot of the current measured between ISE and CE as a function of time as the applied potential difference is varied from-200 mV to +480mV at t-3 s for the 6 ion-selective electrodes of figure 17A;

FIG. 18A shows a schematic of an ion selective electrode cell prepared according to the method of FIG. 1 and a comparative ion selective electrode cellA graph of measured OCP (as measured) over time; and FIG. 18B shows log [ K ] for the ion-selective electrode cell of FIG. 18A and a comparative ion-selective electrode cell⁺]A plot of the OCP as measured of the change;

FIG. 19 shows log [ Mg ] for an ion-selective electrode cell prepared according to the method of FIG. 1 and a comparative ion-selective electrode cell²⁺]A plot of varying OCP as measured; and

fig. 20 shows a graph of OCP as measured over time for an ion selective electrode cell prepared according to the method of fig. 1 and a comparative ion selective electrode cell.

Detailed Description

Method

Fig. 1 schematically depicts a method of making an Ion Selective Electrode (ISE) for an ion selective electrode cell according to an exemplary embodiment. The ion selective electrode cell includes an ISE and a Reference Electrode (RE).

At S101, the ISE and second electrode are exposed to a solution comprising ions.

At S102, a PD of a first set of first Potential Differences (PDs) having a polarity is applied across the ISE and the second electrode.

At S103, a first potential difference PD of opposite polarity in the second group PD is applied across the ISE and the second electrode.

Experiment of

Fig. 2 schematically depicts the method of fig. 1 in more detail.

In particular, provision is made for sensing K as described below⁺The ion selective electrode cell of (1).

Electrode for electrochemical cell

ISE and CE (counter electrode) are provided, at least in part, by using commercially available carbon inks (available from DuPont (RTM) (ink A: BQ242) and Gwent (RTM) (ink B: C2110602D4) and Loctite (ink C: EDAG PF 407A E)&C) Screen printing onto a polymeric substrate, particularly PE. The RE was provided by screen printing onto the polymeric substrate using a commercially available Ag/AgCl ink from Gwent Group (C2130809D 5). ISE, CE and RE are coated with commercially available dielectric inks. I isSE, CE and RE were each 1mm in diameter, and thus the exposed surface area was 0.785mm²。

Electrode functionalization

Polyvinyl Chloride (PVC) 31.3%, dioctyl Sebacate (Bis (2-ethylhexyl) senoate, DOS) 62.3%, potassium tetrakis (4-chlorophenyl) borate (ktpclbb) 1.4%, and validamycin 5% were mixed in cyclohexanone to provide a polymer mixture. These chemicals were obtained from Sigma-aldrich (rtm). Specifically, 66mg of PVC, 143. mu.L of DOS, 3mg of tetrakis (4-chlorophenyl) borate, and 10mg of valinomycin were mixed in 1mL of cyclohexanone. 0.3 μ l of the polymer mixture was deposited on screen-printed carbon for ISE to provide a polymer layer with a thickness of about 10 to 20 μm. The ion selective electrode cell was dried on a hot plate at 50 ℃ for 2 hours, transferred to an airtight container with desiccant and stored in the dark until use. Alternatively, the ion selective electrode cell may be air-dried.

Measuring process

Standard potentiometer measurement of ISE to RE potential

A comparative example ion-selective electrode cell not prepared according to the method of the first aspect was used to determine the presence of ions in solution. The dry sensor (i.e., without conventional conditioning) with the deposited PVC ion selective membrane was immersed in PBS containing 2mM potassium. After a 9 second delay, the OCP was measured for 50 seconds. The final potential difference between ISE and RE is measured every 1 second.

The presence of ions in solution was determined using an exemplary ion selective electrode cell prepared according to the method of the first aspect. In particular, a negative potential difference is applied across the ISE and the second electrode, followed by a positive potential difference. In more detail, a dry sensor (i.e., without conventional conditioning) with a deposited PVC ion selective membrane was immersed in PBS containing 2mM potassium. After a 2 second delay, the potential difference between ISE and RE is stepped (step) between-200 mV (hold 3 seconds) and +190mV (hold 3 seconds). After an additional 1 second delay (i.e., 9 seconds total, as for the comparative example ion selective electrode cell), the OCP50 seconds were measured again. The final potential difference between the ion selective SPE and the printed Ag/AgCl was measured and sampled every 1 second. The final potential difference between ISE and RE is measured every 1 second.

Fig. 3 shows a graph of measured OCP over time for an ion-selective electrode cell prepared according to the method of fig. 1 using ink a and a comparative ion-selective electrode cell. K⁺Concentration of (A) [ K ]⁺]Was 2 mM.

The measured OCP for the ion selective electrode cell of the comparative example was asymptotically stable for at least 40s (seconds) or 45 s. In contrast, the measured OCP of the exemplary ion-selective electrode cell prepared as described above stabilized within 5s or less. In addition, since the response time of the ion selective electrode cell including the prepared ISE is improved, more measurements can be made while the signal is stable, thereby improving, for example, the Relative Standard Deviation (RSD) of the measurements.

Fig. 4A and 4B show log [ K ] of ion-selective electrode cells (E1A, E2A, and E3A) prepared according to the method of fig. 1 and comparative ion-selective electrode cells (CE1A and CE2A) using ink a⁺]Graphs of the measured OCP (as measured and normalized, respectively) of the changes. For log [ K ]⁺]Normalized OCP was normalized to measured OCP by 0.3. The ion-selective electrode cells (E1A, E2A and E3A) prepared according to the method of FIG. 1 were immersed in K⁺Concentration [ K ]⁺]Prepared in situ in 2mM aqueous solution. Thereafter, OCP was measured, and then, K was sequentially increased while stirring⁺Concentration of (A) [ K ]⁺]The OCP was measured at each concentration. The OCP of the comparative ion-selective electrode cells (CE1A and CE2A) were similarly measured at continuous concentrations, and the comparative ion-selective electrode cells had been immersed in the solution prior to the first measurement for the time corresponding to the preparation of fig. 1. The comparative ion selective electrode cell exhibited a greater Nernsian response, whereas the ion selective electrode cell prepared according to the method of FIG. 1 exhibited a relatively greater Nernsian response.

Ion selective electrode cell	m	c	R2
				CE1A	0.0886	0.0227	0.9837
CE2A	0.0883	-0.0246	0.9958
				E1A	0.0776	-0.0235	0.9996
E2A	0.0621	-0.0186	0.9992
				E3A	0.0492	-0.0173	0.9754

Table 1: type y-mx + c and R for the graph of fig. 4B²The best fit line of (c).

FIGS. 5A and 5B show diagrams according to the use of ink BLog [ K ] of ion selective electrode cells (E1B, E2B and E3B) prepared by the method of 1 and comparative ion selective electrode cells (CE1B and CE2B)⁺]Graphs of the measured OCP (as measured and normalized, respectively) of the changes. For log [ K ]⁺]The normalized OCP was normalized for the measured OCP by 0.3. The ion-selective electrode cells (E1B, E2B and E3B) prepared according to the method of FIG. 1 were immersed in K⁺Concentration [ K ]⁺]Prepared in situ in 2mM aqueous solution. Thereafter, OCP was measured, and then, K was sequentially increased while stirring⁺Concentration of (A) [ K ]⁺]The OCP was measured at each concentration. The OCP of the comparative ion-selective electrode cells (CE1B and CE2B) were similarly measured at continuous concentrations, and the comparative ion-selective electrode cells had been immersed in the solution prior to the first measurement for the time corresponding to the preparation of fig. 1. The comparative ion selective electrode cell exhibited a less than nernst response, while the ion selective electrode cell prepared according to the method of fig. 1 exhibited a relatively greater nernst response.

Ion selective electrode cell	m	c	R2
				CE1B	0.0259	-0.0065	0.9707
CE2B	0.0329	-0.0084	0.9791
				E1B	0.0421	-0.0117	0.9947
E2B	0.0532	-0.016	0.9987
				E3B	0.0517	-0.0149	0.9986

Table 2: type y-mx + c and R for the graph of fig. 5B²The best fit line of (c).

Fig. 6A and 6B show log [ K ] of ion-selective electrode cells (E1C, E2C, and E3C) prepared according to the method of fig. 1 and comparative ion-selective electrode cells (CE1C and CE2C) using ink C⁺]Graphs of the measured OCP (as measured and normalized, respectively) of the changes. For log [ K ]⁺]Normalized for OCP normalized for the measured OCP 0.3. The ion-selective electrode cells (E1C, E2C and E3C) prepared according to the method of FIG. 1 were immersed in K⁺Concentration [ K ]⁺]Prepared in situ in 2mM aqueous solution. Thereafter, OCP was measured, and then, K was sequentially increased while stirring⁺Concentration of (A) [ K ]⁺]The OCP was measured at each concentration. The OCP of the comparative ion-selective electrode cells (CE1C and CE2C) were similarly measured at continuous concentrations, and the comparative ion-selective electrode cells had been immersed in the solution prior to the first measurement for the time corresponding to the preparation of fig. 1. Comparative ion-selective electrode cells exhibited less than Nernst responseThe ion selective electrode cell prepared according to the method of fig. 1 exhibits a relatively greater nernst response.

Ion selective electrode cell	m	c	R2
				CE1C	0.0315	-0.0115	0.9724
CE2C	0.0349	-0.0122	0.984
				E1C	0.0305	-0.0099	0.9942
E2C	0.05	-0.0149	0.9954
				E3C	0.0444	-0.0139	0.9982

Table 3: type y-mx + c and R for the graph of fig. 6B²The best fit line of (c).

In particular, fig. 4-6 are for three different commercially available carbon inks.

As shown in table 4, the exemplary ion-selective electrode cell prepared as described above exhibited improved linearity and greater nernst response as compared to the comparative ion-selective electrode cell. Whereas for the comparative ion-selective electrode cell, different carbon inks A, B, C produced different non-nernst responses, the example ion-selective electrode cell prepared as described herein produced a greater nernst response. Without being bound by any theory, the preparation method provides an ion selective electrode cell that is relatively more balanced with solution than the comparative examples.

Table 4: r of the exemplary ion-selective electrode cell and the comparative ion-selective electrode cell²。

Fig. 7 shows a graph of the current measured between ISE and CE for an ion selective electrode cell prepared according to the method of fig. 1.

The current measured between ISE and CE while applying the potential difference can be used to identify whether all electrodes in a batch perform similarly.

For example, the example ion-selective electrode cell S2B7 exhibited a greater current than the other two example ion-selective electrode cells. Further, during the measurement, the example ion selective electrode cell S2B7 was for the same K⁺The concentration also has the greatest potential.

Carbon coverage effect of polymer mixtures

FIG. 17A shows a sensor for sensing K prepared according to the method of FIG. 1⁺6 ion selective electrodesPhotographs of batteries (H15 and H9; F14 and E14; and E4 and F15). These ISE cells were typically prepared as described with respect to fig. 2 using 31.3% polyvinyl chloride (PVC), 62.3% dioctyl sebacate (DOS), 1.4% potassium tetrakis (4-chlorophenyl) borate, and 5% valinomycin in cyclopentanone/propiophenone (3:1) on SPE sensors. Instead, the deposition of the polymer mixture is controlled such that: i. h15 and H9: the polymer mixture had poor coverage of screen printed carbon (coverage of carbon about 50%); ii. F14 and E14: the polymer mixture partially covered the screen printed carbon (approximately 80% coverage of carbon); and iii, E4 and F15: the polymer mixture completely covered the screen printed carbon (100% coverage of carbon). For the ion selective electrode ISE, the perimeter of the polymer mixture P is shown as a white dashed line and the perimeter of the carbon C is shown as a white dotted line. The periphery of the Ag reference electrode RE is shown as a black dashed line.

Fig. 17B shows a plot of the current measured between ISE and CE over time as the applied potential difference is changed from-200 mV to +480mV at t 3s for the 6 ion-selective electrodes of fig. 17A (H15 and H9; F14 and E14; and E4 and F15). In particular, fig. 17B shows that the measured current spike (i.e., instantaneous current increase) when changing the potential difference can be used as an indication of the coverage of the carbon by the polymer mixture, and thus for quality control of ISE batteries. For H15 and H9 (poor coverage), a current spike of about 0.8 μ Α was measured, where the current decayed to steady state within about 2 s. For F14 and E14 (partial coverage), a current spike of about 0.3 μ Α was measured, where the current decayed to steady state within about 1.5 s. For E4 and F15 (full coverage), the current spike was less than 0.05 μ Α, with the current decaying to steady state within about 0.5 s.

Use of polyurethanes comprising ionophores

Fig. 18A shows a plot of measured OCP (as measured) over time for an ion selective electrode cell (suffix prec200) prepared according to the method of fig. 1 and a comparative ion selective electrode cell. These ISE cells were typically prepared as described with respect to fig. 2 using PU (Aldrich option) 31.3%, dioctyl sebacate (DOS) 62.3%, potassium tetrakis (4-chlorophenyl) borate 1.4%, and potassium ionophore 5% in cyclopentanone/propiophenone (6:1) on an SPE sensor. In contrast, the polymer mixture comprises Polyurethane (PU) instead of PVC. In addition, during the measurement, the potential difference between ISE and RE was stepped between-200 mV (hold 3s) and +200mV (hold 3s) after a 1s delay. Figure 18A shows that ion selective electrode cells prepared according to the method of figure 1 exhibit OCP stability that is reproducible over time. In contrast, the OCP of the comparative example continuously increased during the measurement, and the reproducibility was poor. That is, the time to reach a stable signal is reduced by this exemplary method.

FIG. 18B shows log [ K ] for the exemplary ion-selective electrode cell of FIG. 18A and a comparative ion-selective electrode cell⁺]Graph of varying OCP as measured. The potential difference between ISE and RE was stepped between-200 mV (hold 1s) and +800mV (hold 5 s). In particular, for the exemplary ion selective electrode cell (open mark), a supernernst reaction, K, was observed⁺Ion Activity a_IThe x10 change of (a) results in a significantly larger change in the potential E for the monovalent K⁺The ion was about 154 mV. In contrast, this response of the comparative example is for K⁺Ion Activity a_IX10 of (a) was varied to about 52 mV. That is, the exemplary method can induce a super-Nernst response (signal of greater slope versus log _ concentration) to increase sensitivity, which is important for measuring small differences in concentration. To achieve this, different magnitudes of preconditioning voltages may be employed, and these voltages may be optimized for various polymer/membrane compositions.

Use of urethane acrylates with acrylic monomers including ionophores

An ion-selective electrode cell and a comparative ion-selective electrode cell were prepared according to the method of fig. 1. These ISE cells are typically prepared as described with respect to fig. 2 using UV curable resins ancubic, dioctyl sebacate, potassium tetrakis (4-chlorophenyl) borate, valinomycin (36.6%, 59.7%, 1.4%, 2.3% w/w). In contrast, the polymer mixture includes a UV curable urethane acrylate with an acrylic monomer instead of PVC.

Table 5: r of the exemplary ion-selective electrode cell and the comparative ion-selective electrode cell². Linearity (R) of exemplary ion-selective electrode cells compared to comparative ion-selective electrode cells²) Is improved.

Magnesium alloy

FIG. 19 shows log [ Mg ] of ion-selective electrode cells (F2, F21, F4) prepared according to the method of FIG. 1 and comparative ion-selective electrode cells (F6, F23, F24)²⁺]Graph of varying OCP as measured. These ISE cells were typically prepared as described with respect to fig. 2, using PVC, DOS, KTpClFB, Mg ionophore I (32.4%, 64.1%, 1.5%, 2% w/w) in cyclopentanone/propiophenone (4:1) on SPE sensors. In contrast, the ionophore was Mg ionophore I rather than valinomycin. Mg (magnesium)²⁺Is in the biologically relevant range of 0.5mM to 1.25 mM.

Table 6: r of the exemplary ion-selective electrode cell and the comparative ion-selective electrode cell²And a gradient. The exemplary ISE cells (F2, F21, F4) exhibited approximately nernst response (based on gradient) with improved linearity (R) compared to the comparative examples²) And reproducibility.

FIG. 20 shows a plot of OCP as measured over time for an ion-selective electrode cell (suffix PREC200-200) prepared according to the method of FIG. 1 and a comparative ion-selective electrode cell. These ISE cells were typically prepared as described with respect to fig. 2 using PVC, NPOE (1- (2-Nitrophenoxy) octane, 1- (2-Nitrophenoxy) octane), NaTFBP, Mg ionophore I (32.8%, 65.7%, 0.5%, 1% w/w) in cyclopentanone/propiophenone (4:1) on SPE sensors. In particular, for the exemplary ISE battery, less drift in the measurement duration is observed. Fig. 8 schematically depicts an ion selective electrode cell according to an exemplary embodiment. In particular, as described above, the ion selective electrode cell includes ISE and RE, and is depicted in a circuit with a potentiostat. In general, a potentiostat is the electronic hardware required to control a three-electrode cell and run most electroanalytical experiments. The double potentiostat and the multiple potentiostats are potentiostats capable of respectively controlling two working electrodes and more than two working electrodes. Potentiostats function by adjusting the current at the auxiliary electrode to maintain the potential of the working electrode at a constant level relative to the reference electrode. It consists of a circuit that is usually described in terms of a simple operational amplifier.

Fig. 9 schematically depicts an ion selective electrode cell according to an exemplary embodiment. In particular, as described above, the ion selective electrode cell includes ISE, RE, and CE, and is depicted in a circuit with a potentiostat.

Fig. 10 schematically depicts an electrical circuit of an ion selective electrode cell according to an exemplary embodiment. In particular, fig. 10 shows a potentiostat circuit for a potentiometer. Fig. 11 schematically depicts an electrical circuit of an ion selective electrode cell according to an exemplary embodiment. In particular, fig. 11 shows a potentiostat/galvanostat circuit for a potentiometer/galvanometer.

Fig. 12 schematically depicts an exploded perspective view of an ion selective electrode cell according to an example embodiment. In this example, the ion-selective electrode cell 10 includes ISE 100 and reference electrode RE 200, and counter electrode CE 300 provided by screen printing on a rectangular substrate layer 11. Each electrode is L-shaped and comprises a track provided by the long leg of the L, extending to a first end of the substrate layer 11 for coupling to, for example, a potentiostat. Three corresponding circular holes 121A, 121B, 121C are provided in the mask layer 12 covering the ISE 100, RE 200 and CE 300, exposing circular portions of these respective electrodes, particularly in the respective L-shaped short legs. The channel layer 13 covers the mask layer 12 with a channel 131 extending from a second end of the channel layer 13, which is remote from the first end of the substrate layer, towards an opposite first end of the channel layer 13, whereby the circular holes 121A, 121B, 121C are completely within the channel 131. The cover layer 14 covers the channel layer 13 and includes square holes 141 coinciding with the ends of the channels 131.

Figure 13 schematically depicts an example of applying a potential difference in more detail for the method of figure 1. In example a, equal and opposite constant potential differences are applied alternately, where M-N-2 with a linear ramp in between. In example B, equal and opposite triangular-waveform potential differences are alternately applied, where M-N-2 with a linear ramp in between. In example B, equal and opposite rectangular-waveform potential differences are alternately applied, where M-N-2 with a square ramp in between. In example B, equal and opposite rectangular-waveform potential differences are alternately applied, where M-N-2 with a square ramp and gap in between. As previously mentioned, a first PD of the first set of PDs may include a portion, e.g., a positive portion or a negative portion, of a waveform, e.g., a unidirectional, bidirectional, periodic, non-periodic, symmetric, asymmetric, simple, and/or complex waveform, e.g., a sinusoidal waveform, a rectangular waveform, a square waveform, a pulse waveform, a ramp waveform, a sawtooth waveform, and/or a triangular waveform. Other waveforms are known. In one example, the first set of PDs includes M PDs including the first PD, where M is a natural number of at least 1, such as 1, 2, 3,4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, or more. The M PDs in the first group of PDs may be as described with respect to the first PD in the first group of PDs. Alternatively, the M PDs in the first group of PDs may have mutually different amplitudes and/or durations. The first PD of the second group of PDs and/or the second group of PDs may be as described with respect to the first PD of the first group of PDs and the first group of PDs, respectively. The delay between a PD in the first group of PDs and a PD in the second group of PDs may be as previously described.

Constant potential rectifier

The potentiostat is an electronic instrument that controls the voltage between two electrodes.

Double-electrode structure

FIG. 14A schematically depicts an electrical circuit of an ion selective electrode cell according to an exemplary embodiment; and fig. 14B schematically depicts a potential gradient in the ion selective electrode cell of fig. 14A. In particular, fig. 14A schematically depicts a two-electrode configuration, where EA is the applied voltage and C and W are the counter and working electrodes, respectively; and fig. 14B schematically depicts the potential gradient in a two-electrode system when current flows.

The configuration includes a Working Electrode (WE) in which the chemical process of interest takes place and a Counter Electrode (CE) which serves as the other half of the cell. The applied potential (EA) is measured between the working electrode and the counter electrode, and the resulting current is measured in the working electrode or counter electrode lead.

The CE in the two-electrode arrangement provides two functions. It completes the circuit that allows charge to flow through the battery, and it also maintains a constant interface potential regardless of current. In most cases, meeting these two requirements is an impossible task. In a two-electrode system, it is difficult to maintain a constant CE potential (eC) when a current flows. This fact, together with the lack of compensation for the voltage drop across the solution (iRS), results in poor control of the WE potential (eW) with a two-electrode system. Two separate electrodes serve better for passing current and maintaining a reference voltage.

Three-electrode structure

FIG. 15A schematically depicts an electrical circuit of an ion selective electrode cell according to an exemplary embodiment; and fig. 15B schematically depicts a potential gradient in the ion selective electrode cell of fig. 15A. In particular, fig. 15A schematically depicts a three-electrode configuration, where EA is the applied voltage and W, C and R are the working, counter and reference electrodes, respectively; and fig. 15B schematically depicts the potential gradient in a three-electrode system when current flows.

The three-electrode system remedies many of the problems of the two-electrode configuration. The three-electrode system consists of a working electrode, a counter electrode and a reference electrode. The function of the reference electrode is to serve as a reference in measuring and controlling the potential of the working electrode without passing any current. The reference electrode should have a constant electrochemical potential at low current densities. In addition, the iR drop between the reference electrode and the working electrode (iRU) is typically very small, since the reference electrode passes negligible current. Thus, with a three-electrode system, the reference potential is more stable and iR drop across the solution is compensated. This translates into excellent control of the working electrode potential. The most common laboratory reference electrodes are saturated calomel electrode and Ag/AgCl electrode.

In a three-electrode configuration, the only effect on the electrode is by balancing all of the current required to balance the current observed at the working electrode. The counter electrode is usually swung to a limit potential in order to accomplish this task.

Potentiostat operation

A basic potentiostat can be modeled as an electronic circuit comprising four components: an electrometer, an I/E converter, a control amplifier, and a signal.

Electrostatic meter

Fig. 16 schematically depicts an electrical circuit of an ion selective electrode cell according to an exemplary embodiment. In particular, FIG. 16 shows a block diagram of a typical computer controlled potentiostat system for a three-electrode controlled potential device. X1 on the amplifier indicates a unity gain amplifier.

The electrometer circuit measures the voltage difference between the working electrode and the reference electrode. The output serves two purposes: it acts as a feedback signal in the potentiostat, and I is the voltage signal measured and displayed to the user.

An ideal electrometer has infinite impedance and zero current. In practice, the reference electrode does pass a very small amount of current. The current through the reference electrode can change its potential, but the current is typically so close to zero that the change is negligible.

The capacitance of the electrometer and the resistance of the reference electrode form an RC circuit. If the RC time constant is too large, it may limit the effective bandwidth of the electrometer. The bandwidth of the electrometer must be higher than the bandwidth of all other components in the potentiostat.

I/E converter

The current-to-voltage converter measures the battery current. The battery current is forced through the current measuring resistor Rm. The resulting voltage across the resistor is a measure of the battery current.

The cell current may vary by several orders of magnitude during the course of the experiment. This wide range of currents cannot be accurately measured by a single resistor. Modern potentiostats have multiple Rm resistors and an "l/E self-range" algorithm that selects the appropriate resistor and switches it into an l/E circuit under computer control.

The bandwidth of the I/E converter is very dependent on its sensitivity. The unwanted capacitance in the I/E converter together with Rm forms an RC circuit. In order to measure small currents Rm must be large enough. However, this large resistance increases the RC time constant of the circuit, limiting the I/E bandwidth. For example, 10nA can be measured at 100kHz without a potentiostat.

Control amplifier

The control amplifier compares the measured battery voltage with the desired battery voltage and drives current into the battery to force the voltages to be the same. The control amplifier operates according to the negative feedback principle. The measured voltage enters the amplifier in the negative or inverting input. Thus, a positive disturbance in the measured voltage causes a decrease in the output of the control amplifier, which counteracts the initial change. The control amplifier has a limited output capability, which for Emstat is 3V and 10 mA.

Signal

In modern potentiostats, the signal circuit is a computer-controlled voltage source. Proper selection of the digital sequence allows the computer to produce constant voltages, voltage ramps, and sine waves at the signal current output.

Computer controlled instrument

Most potentiostats now utilize microprocessors to generate signals and acquire data. Computers are very useful for generating complex voltage waveforms. These waveforms are first created in memory as arrays of values, which are sent to digital to analog converters (DACs). The DAC generates an analog voltage proportional to the digital numerical array. The analog voltage is then sent to the control amplifier of the potentiostat.

In contrast, in data acquisition, the voltage response from the electrometer and I/E converter is digitized into an array of values and recorded at fixed time intervals. The accuracy of the analog-to-digital conversion depends on the number of bits used for a given voltage signal. For example, if the measurement system digitizes an input signal of 0V to 10V with 8-bit resolution, it converts the voltage signal into a number in the range of 0-255 according to a binary conversion. Thus, after digitization, a 0V to 10V signal, represented as an 8-bit array, will have a resolution of 10/255 or 39.2 mV.

While preferred embodiments have been shown and described, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined in the following claims and as described above.

In summary, the present invention provides an ion-selective electrode cell for an ion-selective electrode and a method of preparing an ion-selective electrode ISE for an ion-selective electrode cell for an ion-selective electrode.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at most some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.